A beautiful example of humans in the supreme invention and deployment of JWST.
(A reminder that Tuesday is a ‘non-doggie’ day.)
JWST is astounding. It will look back to the beginnings of the universe, just 200 million light-years after the Big Bang, or possibly further back in time. Because of the way that the universe stretches out and causes light to go red, as it were, JWST will be searching for images from the cosmos in the infrared.
I recently listened to a 30-minute programme on BBC Sounds. It was a BBC Discovery episode about the JWST. Recorded before the launch it was, nonetheless, a deeply fascinating programme about what JWST will be looking for.
I wasn’t going to publish a post for today but then yesterday I read this article on The Conversation and wanted to share it with you. In fact it shares much of what I posted on the 1st, The Big Question. Because time and infinity are beautifully connected.
Imagine time running backwards. People would grow younger instead of older and, after a long life of gradual rejuvenation – unlearning everything they know – they would end as a twinkle in their parents’ eyes. That’s time as represented in a novel by science fiction writer Philip K Dick but, surprisingly, time’s direction is also an issue that cosmologists are grappling with.
While we take for granted that time has a given direction, physicists don’t: most natural laws are “time reversible” which means they would work just as well if time was defined as running backwards. So why does time always move forward? And will it always do so?
Does time have a beginning?
Any universal concept of time must ultimately be based on the evolution of the cosmos itself. When you look up at the universe you’re seeing events that happened in the past – it takes light time to reach us. In fact, even the simplest observation can help us understand cosmological time: for example the fact that the night sky is dark. If the universe had an infinite past and was infinite in extent, the night sky would be completely bright – filled with the light from an infinite number of stars in a cosmos that had always existed.
For a long time scientists, including Albert Einstein, thought that the universe was static and infinite. Observations have since shown that it is in fact expanding, and at an accelerating rate. This means that it must have originated from a more compact state that we call the Big Bang, implying that time does have a beginning. In fact, if we look for light that is old enough we can even see the relic radiation from Big Bang – the cosmic microwave background. Realising this was a first step in determining the age of the universe (see below).
But there is a snag, Einstein’s special theory of relativity, shows that time is … relative: the faster you move relative to me, the slower time will pass for you relative to my perception of time. So in our universe of expanding galaxies, spinning stars and swirling planets, experiences of time vary: everything’s past, present and future is relative.
So is there a universal time that we could all agree on?
It turns out that because the universe is on average the same everywhere, and on average looks the same in every direction, there does exist a “cosmic time”. To measure it, all we have to do is measure the properties of the cosmic microwave background. Cosmologists have used this to determine the age of the universe; its cosmic age. It turns out that the universe is 13.799 billion years old.
So we know time most likely started during the Big Bang. But there is one nagging question that remains: what exactly is time?
To unpack this question, we have to look at the basic properties of space and time. In the dimension of space, you can move forwards and backwards; commuters experience this everyday. But time is different, it has a direction, you always move forward, never in reverse. So why is the dimension of time irreversible? This is one of the major unsolved problems in physics.
To explain why time itself is irreversible, we need to find processes in nature that are also irreversible. One of the few such concepts in physics (and life!) is that things tend to become less “tidy” as time passes. We describe this using a physical property called entropy that encodes how ordered something is.
Imagine a box of gas in which all the particles were initially placed in one corner (an ordered state). Over time they would naturally seek to fill the entire box (a disordered state) – and to put the particles back into an ordered state would require energy. This is irreversible. It’s like cracking an egg to make an omelette – once it spreads out and fills the frying pan, it will never go back to being egg-shaped. It’s the same with the universe: as it evolves, the overall entropy increases.
It turns out entropy is a pretty good way to explain time’s arrow. And while it may seem like the universe is becoming more ordered rather than less – going from a wild sea of relatively uniformly spread out hot gas in its early stages to stars, planets, humans and articles about time – it’s nevertheless possible that it is increasing in disorder. That’s because the gravity associated with large masses may be pulling matter into seemingly ordered states – with the increase in disorder that we think must have taken place being somehow hidden away in the gravitational fields. So disorder could be increasing even though we don’t see it.
But given nature’s tendency to prefer disorder, why did the universe start off in such an ordered state in the first place? This is still considered a mystery. Some researchers argue that the Big Bang may not even have been the beginning, there may in fact be “parallel universes” where time runs in different directions.
Will time end?
Time had a beginning but whether it will have an end depends on the nature of the dark energy that is causing it to expand at an accelerating rate. The rate of this expansion may eventually tear the universe apart, forcing it to end in a Big Rip; alternatively dark energy may decay, reversing the Big Bang and ending the Universe in a Big Crunch; or the Universe may simply expand forever.
But would any of these future scenarios end time? Well, according to the strange rules of quantum mechanics, tiny random particles can momentarily pop out of a vacuum – something seen constantly in particle physics experiments. Some have argued that dark energy could cause such “quantum fluctuations” giving rise to a new Big Bang, ending our time line and starting a new one. While this is extremely speculative and highly unlikely, what we do know is that only when we understand dark energy will we know the fate of the universe.
So what is the most likely outcome? Only time will tell.
Let me explain, in part, entropy. Because while I and many others sort of understand it, the principle behind entropy is much more detailed.
It is explained pretty well on WikiPedia, from which I reproduce the first paragraph.
Life is without meaning. You bring the meaning to it.
The meaning of life is whatever you ascribe it to be.
Being alive is the meaning.
On the 28th March I wrote what I thought was a concluding piece on the subject of ‘meaning’. I used some of the most amazing details about the universe to highlight the fact that, in the end, if our civilisation doesn’t get it’s collective act together then from the perspective of the universe it is all pretty irrelevant. In that piece I quoted from Prof. Brian Cox, “Everything we are, everything that’s ever been and everything that will ever be was all forged in the same moment of creation 13.7bn years ago from an unimaginably hot and dense volume of matter less than the size of an atom.”
Now, in fairness, Prof. Cox did allude to scientists exploring the notion of what might have happened before the Big Bang. Anyway, a couple of nights ago we watched a BBC Horizon programme, now on YouTube, that looked much more closely into this fascinating topic. The link came to us from the website Top Documentary Films that set out the introduction to the BBC programme.
They are the biggest questions that science can possibly ask: where did everything in our universe come from? How did it all begin? For nearly a hundred years, we thought we had the answer: a big bang some 14 billion years ago.
But now some scientists believe that was not really the beginning. Our universe may have had a life before this violent moment of creation.
Horizon takes the ultimate trip into the unknown, to explore a dizzying world of cosmic bounces, rips and multiple universes, and finds out what happened before the big bang.
Answer: Instead of the universe inexplicably springing into existence from a mysteriousinitial singularity, the Big Bang was a collision between two universes like ours existing as parallel membranes floating in a higher-dimensional space that we’re not aware of.
One bang is followed by another, in a potentially endless series of cosmic cycles, each one spelling the end of a universe and the beginning of a new one. Not one bang, but many.
Sir Roger Penrose has changed his mind about the Big Bang. He now imagines an eternal cycle of expanding universes where matter becomes energy and back again in the birth of new universes and so on and so on.
I have referred yesterday to the series on the BBC hosted by Professor Brian Cox called Wonders of the Universe. Well we managed to watch the last episode last night, entitled Messengers. Like the other three episodes, it was breath-taking.
In this last episode, Prof. Cox speaks of the universe still expanding with the outer edge, if edge is the appropriate word, being about 8.7 billion light years away. Thus the age of the Universe is about that; 8.7 billion light years. Note: NASA has a piece that suggests that this figure may not be confirmed. But let’s not worry too much about the precise value. But we will take a short detour to understand a little more about the ‘light year’.
So to measure really long distances, people use a unit called alight year. Light travels at 186,000 miles per second (300,000 kilometers per second). Therefore, a light second is 186,000 miles (300,000 kilometers). A light year is the distance that light can travel in a year, or:
A light year is 5,865,696,000,000 miles (9,460,800,000,000 kilometers). That’s a long way!
That is a single light-year. Now reflect on the outer edge of the universe being, say, 8,700,000,000 multiplied by 5,865,696,000,000 miles away. Don’t know about your mind, but my mind has no ‘feel’ for that distance whatsoever.
OK, next proposition put forward by Prof. Cox. That is that scientists believe that ‘The Big Bang’ was the instant that the universe erupted, if that’s an appropriate word, from a single point, smaller than the size of a grain of sand.
That has no rational meaning whatsoever. Now my mind just goes into la, la land! But at the level of magic, mysticism, the spiritual, then one does experience the deep meaning of the creation. Our creation. For we are part of the universe and the universe is part of us.
Just like the rose. Trying to describe it cuts nothing compared to closing one’s eyes and simply breathing in the perfume.
Here is that last episode, in four parts from YouTube. Watch and prepared to be transformed.